Thermal fracture of functionally graded plate with parallel surface cracks

Abstract

This work examines the fracture behavior of a functionally graded material (FGM) plate containing parallel surface cracks with alternating lengths subjected to a thermal shock. The thermal stress intensity factors (TSIFs) at the tips of long and short cracks are calculated using a singular integral equation technique. The critical thermal shock ΔTc that causes crack initiation is calculated using a stress intensity factor criterion. Numerical examples of TSIFs and ΔTc for an Al2O3/Si3N4 FGM plate are presented to illustrate the effects of thermal property gradation, crack spacing and crack length ratio on the TSIFs and ΔTc. It is found that for a given crack length ratio, the TSIFs at the tips of both long and short cracks can be reduced significantly and ΔTc can be enhanced by introducing appropriate material gradation. The TSIFs also decrease dramatically with a decrease in crack spacing. The TSIF at the tips of short cracks may be higher than that for the long cracks under certain crack geometry conditions. Hence, the short cracks instead of long cracks may first start to grow under the thermal shock loading.